Abstract 2236: A selection strategy for the design of small proteins that can distinguish DNA repair intermediates.

Abstract

Abstract Recognition of DNA damage by repair proteins is crucial for genomic stability. Several repair enzymes recognize aberrant DNA structural features, including nicks, gaps, and abasic sites, in a sequence-independent DNA manner. Reported here is a strategy to model these protein-DNA interactions using small proteins. A phage-displayed library of approximately one hundred million distinct zinc fingers was engineered at the DNA level based on the DNA binding domain of the repair protein poly(ADP-ribose) polymerase. Eight codons, representing amino acid residues in ‘loop’ regions of the zinc finger structure, were randomized using an NNK codon scheme. The DNA cassette was cloned into a commercially obtained T7 phagemid vector. The resultant phage library was exposed to nicked DNA molecules, which were attached to magnetic beads via a biotin-streptavidin linkage. In four rounds of selection that featured negative selection against non-nicked DNA and streptavidin coated beads, viral retention on the affinity resin increased from a negligible quantity to 62%. DNA sequencing following the final round revealed near convergence to a single, 39-mer peptide. This selected peptide will be generated by bacterial expression and assayed for binding activity using multiple strategies. While phage display of sequence specific DNA binding proteins is well-precedented, selection of peptides that bind specific DNA structures has not been reported. Molecules discovered by this strategy will help illuminate the structure-function relationships of proteins that recognize distinct DNA structures and may lead to new anticancer approaches. Citation Format: Rachel M. Guerra, Kristina M. Langenborg, Kayla M. Gross, Emily V. Sher, John W. Gilboy, Dylan Plaskon, Kevin P. Rice. A selection strategy for the design of small proteins that can distinguish DNA repair intermediates. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2236. doi:10.1158/1538-7445.AM2013-2236